The automatic implantable cardioverter defibrillator (AICD or "implantable cardioverter defibrillator") is a device used in the treatment of a class of patients prone to life threatening tachycardias. Currently, implantable cardioverter defibrillators classify signals derived from a single channel; a ventricular sensing electrode. Many single channel intracardiac electrographic classification methods have been proposed, including frequency domain analysis, gradient pattern detection, sequential testing, median frequency, correlation waveform analysis, the Bin area method and neural networks. However, they have been found to be unreliable in their classification of many common tachycardias. This often causes inappropriate therapy to be delivered by the implantable cardioverter defibrillator. Many of the incorrect classifications made by current devices are caused by the overlap of heart rate ranges between sinus tachycardia (ST), supraventricular tachycardia (SVT) and ventricular tachycardia (VT).
Previous work on the classification of intracardiac electrogram signals derived from two channels have concentrated on the analysis of timing sequences. These studies show that the addition of an atrial sensing electrode can greatly improve the reliability of the classification, when compared with classification using a single intracardiac lead.
The improvements are especially marked in differentiating between supraventricular tachycardia (SVT), sinus tachycardia (ST), and ventricular tachycardia (VT). Tachycardias with timing similar to normal sinus rhythm (NSR) such as ventricular tachycardia with 1.1 retrograde conduction (VT 1:1) cannot be identified using these techniques. However, morphological considerations can often resolve this distinction.